Unfortunately, processing of crude fractions may cause the release of byproducts, such as hydrocarbons, hydrogen sulfide, nitrogen oxide and carbon monoxide. These byproducts are formed in a number of ways. For example H2S may be formed as a result of sulfur additions used during crude fraction processing or as a result of sulfur present in the crude fraction being processed, such as sour crude fractions, for example.
Such byproducts are regulated by the Environmental Protection Agency and are subject to the best available control technology (BACT), such as incineration. However, incineration generally oxidizes heterosulfur organic compounds and hydrogen sulfide, generating oxides of sulfur (SOx). Further, many countries, including the United States, have set standards and regulations to control the maximal permissible discharge level of pollutants, such as SOx, to protect the environment.
Further, combustion of heavy fuel oils may generate SOx emissions through the combustion of hydrogen sulfide present in the heavy fuel oils. One method to reduce such emissions includes cleaning the effluent with expensive caustic scrubber equipment. Such scrubbers require extensive initial capital costs and significant annual operating costs. Further, such scrubbing processes generally result in undesirable byproducts, such as sodium and potassium sulfides, sulfites and sulfates, all of which require special handling for disposal.
In addition, sulfur may cause corrosion in pipelines, pumping and refining equipment, poisoning of catalysts used in the refining and combustion of fossil fuels and the premature failure of combustion engines. Sulfur further poisons the catalytic converters used in diesel-powered trucks and buses to control the emissions of oxides of nitrogen (NOx.) Sulfur also causes an increase in particulate emissions from trucks and buses by degrading the soot traps used on these vehicles. Further, the burning of sulfur-containing fuel produces sulfur dioxide (SO2), which enters the atmosphere as acid rain, inflicting harm on agriculture and wildlife and causes hazards to human health. Therefore, removal of sulfur from crude fractions may be desirable.
One method of crude fraction desulfurization is hydrodesulfurization, i.e., the reaction between the fossil fuel and hydrogen gas at elevated temperature and pressure in the presence of a catalyst. This causes the reduction of organic sulfur to gaseous H2S, which is then oxidized to elemental sulfur. However, a large amount of unreacted H2S remains.
Therefore, a need exists for a method of reducing sulfur based emissions from crude fractions, such as asphalt and heavy fuel oil, without the need for intensive capital expenditure.